Factors adversely affecting bone accrual during adolescence may be risk factors for developing osteoporosis later in life. The present review discusses pregnancy and lactation during adolescence as potential conditions negatively affecting bone mass acquisition in women. The physiological adaptations of calcium homeostasis during pregnancy and lactation have been extensively studied in adult women and include a temporary bone loss that is recovered after weaning. Much less is known about the ability of adolescent women to adapt to the high calcium demands of pregnancy and lactation while preserving maternal bone mass. Physiological adaptations of calcium and bone metabolism during adolescence, and during pregnancy and lactation in adolescents are reviewed in this work, with emphasis on intestinal absorption, urinary excretion, bone turnover and hormonal regulation. Comparisons between adult and adolescent women are included. Genetic and nutritional factors potentially affecting bone acquisition during adolescence are considered. The available evidence suggests that pregnancy and lactation adversely affect bone mass acquisition of adolescent women, particularly when calcium intake is low. However, more studies are needed to evaluate the impact of pregnancy and lactation during adolescence on maternal bone mass later in life.